The M'zab is a valley in the northern Sahara in the Ghardaïa wilaya "province" of Algeria, around 500 km south of Algiers. The region was annexed by the French in 1882, becoming part of their North African colonies. At its centre is Ghardaia, a cluster of five medieval walled settlements located on rocky outcrops, each centred round a fortress-like mosque, whose minaret also operates a watchtower. Ghardaia is one of the major oasis groups of the Sahara desert and life there was correspondingly strict, insular and traditional.